Communication control device, communication control method, and terminal device

ABSTRACT

To enable a reduction in the effect of backhauling on wireless communications in the case of carrier aggregation, provided herein is a communication control device that acquires information about a terminal device that uses one component carrier of a macro cell as a primary component carrier, sets one or more component carriers of a small cell partially or fully overlapping with the macro cell as an additional component carrier to be used additionally by the terminal device, and sets one component carrier among the one or more component carriers as a special component carrier on which the terminal device is able to transmit uplink control information on an uplink control channel, wherein the uplink control information includes at least one of an acknowledgement (ACK) and a negative acknowledgement (NACK) regarding reception of a downlink signal, an uplink scheduling request, or periodically reported channel state information.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.15/921,043, filed Mar. 14, 2018, which is a continuation of U.S.application Ser. No. 15/022,139, filed Mar. 15, 2016 (now U.S. Pat. No.9,949,240), which is based on PCT filing PCT/JP2014/074004, filed Sep.10, 2014, and claims priority to JP 2013-242831, filed on Nov. 25, 2013,the contents of each of which are incorporated herein by reference intheir entirety.

TECHNICAL FIELD

The present disclosure relates to a communication control device, acommunication control method, and a terminal device.

BACKGROUND ART

Currently, 4G wireless communication systems are being standardized bythe Third Generation Partnership Project (3GPP). Carrier aggregation isbeing standardized as a technology of 4G wireless communication systems,for example. Carrier aggregation enables the handling of wider bandwidthby collectively handling two or more component carriers (CCs) having aprescribed bandwidth each.

For example, Non-Patent Literature 1 discloses a procedure for adding orremoving a CC to be used by a terminal device in carrier aggregation.

CITATION LIST Non-Patent Literature

Non-Patent Literature 1: 3GPP TS 36.331 V11.0.0 (2012-06) 3rd GenerationPartnership Project; Technical Specification Group Radio Access Network;Evolved Universal Terrestrial Radio Access (E-UTRA); Radio ResourceControl (RRC); Protocol specification (Release 11)

SUMMARY OF INVENTION Technical Problem

A terminal device may use a macro cell CC and a small cell CC forcarrier aggregation. In this case, the terminal device uses the CC ofthe macro cell as a primary component carrier (PCC), and uses the CC ofthe small cell as a secondary component carrier (SCC), for example.Additionally, an uplink control signal (such as an ACK/NACK, forexample) for the SCC (that is, the CC of the small cell) may betransmitted by the PCC (that is, the CC of the macro cell). Furthermore,for example, the uplink control signal may be transmitted from a basestation of the macro cell to a base station of the small cell viabackhauling.

However, in cases like the above, there is a possibility that thewireless communication of the terminal device may be greatly affected bythe backhaul. For example, the uplink control signal (such as anACK/NACK, for example) may take a large amount of time to reach the basestation of the small cell because of a delay on the backhaul. As aresult, operation by the base station of the small cell based on theuplink control signal may be delayed, and communication quality for theterminal device may be lowered.

Accordingly, it is desirable to provide a mechanism enabling a reductionin the effect of backhauling on wireless communications in the case ofcarrier aggregation.

Solution to Problem

According to the present disclosure, there is provided a communicationcontrol device including: an acquisition unit configured to acquireinformation about a terminal device that uses one component carrier of amacro cell as a primary component carrier; and a control unit configuredto set one or more component carriers of a small cell partially or fullyoverlapping with the macro cell as an additional component carrier to beused additionally by the terminal device. The control unit sets onecomponent carrier among the one or more component carriers as a specialcomponent carrier on which the terminal device is able to transmituplink control information on an uplink control channel.

According to the present disclosure, there is provided a communicationcontrol method including: acquiring information about a terminal devicethat uses one component carrier of a macro cell as a primary componentcarrier; and setting, by a processor, one or more component carriers ofa small cell partially or fully overlapping with the macro cell as anadditional component carrier to be used additionally by the terminaldevice. The setting of the one or more component carriers as theadditional component carrier includes setting one component carrieramong the one or more component carriers as a special component carrieron which the terminal device is able to transmit uplink controlinformation on an uplink control channel.

According to the present disclosure, there is provided a terminal deviceincluding: an acquisition unit configured to acquire, when the terminaldevice uses one component carrier of a macro cell as a primary componentcarrier, one or more component carriers of a small cell partially orfully overlapping with the macro cell are set as an additional componentcarrier to be used additionally by the terminal device, and onecomponent carrier among the one or more component carriers is set as aspecial component carrier on which the terminal device is able totransmit uplink control information on an uplink control channel,information about the one component carrier; and a control unitconfigured to control wireless communication on the one componentcarrier so that the uplink control information is transmitted on theuplink control channel of the one component carrier.

Advantageous Effects of Invention

According to the present disclosure as described above, it is possibleto reduce the effect of backhauling on wireless communications in thecase of carrier aggregation. Note that the above advantageous effect isnot strictly limiting, and that any advantageous effect indicated in thepresent disclosure or another advantageous effect that may be reasonedfrom the present disclosure may also be exhibited in addition to, orinstead of, the above advantageous effect.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory diagram for illustrating an example of the PCCsof respective UEs.

FIG. 2 is a first explanatory diagram for illustrating an example of aprocedure after the detection of a radio link failure (RLF).

FIG. 3 is a second explanatory diagram for illustrating an example of aprocedure after the detection of a radio link failure (RLF).

FIG. 4 is an explanatory diagram for illustrating an example of ascenario in which separate frequency bands are used by a macro cell anda small cell.

FIG. 5 illustrates a schematic configuration of a communication systemaccording to an embodiment of the present disclosure.

FIG. 6 illustrates an example of a configuration of a macro base stationaccording to the embodiment.

FIG. 7 is an explanatory diagram for illustrating an example of settinga sub PCC.

FIG. 8 is an explanatory diagram for illustrating an example of settingan SCC associated with a sub PCC.

FIG. 9 is an explanatory diagram for illustrating an example of settingan SCC associated with a PCC.

FIG. 10 is a block diagram illustrating an example of a configuration ofa terminal device according to the embodiment.

FIG. 11 is a flowchart illustrating an example of a diagrammatic flow ofa process related to setting an additional CC according to theembodiment.

FIG. 12 is a flowchart illustrating a first example of a diagrammaticflow of a connection reconfiguration procedure according to theembodiment.

FIG. 13 is a flowchart illustrating a second example of a diagrammaticflow of a connection reconfiguration procedure according to theembodiment.

FIG. 14 is a flowchart illustrating a third example of a diagrammaticflow of a connection reconfiguration procedure according to theembodiment.

FIG. 15 is an explanatory diagram for illustrating an example ofchanging a sub PCC and associating an SCC.

FIG. 16 is a flowchart illustrating an example of a diagrammatic flow ofa connection reconfiguration procedure according to a first modificationof the embodiment.

FIG. 17 is an explanatory diagram for illustrating a first example of aseries of operations related to the occurrence of a radio link failure(RLF).

FIG. 18 is an explanatory diagram for illustrating a second example of aseries of operations related to the occurrence of a radio link failure(RLF).

FIG. 19 is an explanatory diagram for illustrating a third example of aseries of operations related to the occurrence of a radio link failure(RLF).

FIG. 20 is an explanatory diagram for illustrating a fourth example of aseries of operations related to the occurrence of a radio link failure(RLF).

FIG. 21 is a flowchart illustrating an example of a diagrammatic flow ofa connection re-establishment procedure according to a secondmodification of the embodiment.

FIG. 22 is a block diagram illustrating a first example of a schematicconfiguration of an eNB according to an embodiment of the presentdisclosure may be applied.

FIG. 23 is a block diagram illustrating a second example of a schematicconfiguration of an eNB according to an embodiment of the presentdisclosure may be applied.

FIG. 24 is a block diagram illustrating an example of a schematicconfiguration of a smartphone according to an embodiment of the presentdisclosure may be applied.

FIG. 25 is a block diagram illustrating an example of a schematicconfiguration of a car navigation apparatus according to an embodimentof the present disclosure may be applied.

DESCRIPTION OF EMBODIMENTS

Hereinafter, preferred embodiments of the present disclosure will bedescribed in detail and with reference to the attached drawings. Notethat, in this specification and the appended drawings, structuralelements that have substantially the same function and structure aredenoted with the same reference numerals, and repeated explanation ofthese structural elements is omitted.

Hereinafter, the description will proceed in the following order.

1. Introduction

2. Schematic configuration of communication system3. Configuration of macro base stations4. Terminal device configuration5. Process flow

6. Modifications

6.1. First modification

6.2. Second modification

7. Applications

7.1. Application Examples Regarding Base Station

7.2. Application Examples Regarding Terminal Apparatus

8. Conclusion 1. INTRODUCTION

First, FIGS. 1 to 3 will be referenced to describe carrier aggregationin Release 10, a small cell anticipated by Release 12, backhaulingbetween eNBs, and the conditions of backhauling for carrier aggregation.

(Carrier Aggregation in Release 10)

Component Carriers

With carrier aggregation in Release 10, up to a maximum of fivecomponent carriers (CCs) are aggregated for use by user equipment (UE).Each CC is a band with a maximum width of 20 MHz. Carrier aggregationincludes a case in which successive CCs in the frequency direction areused, and a case in which separated CCs in the frequency direction areused. With carrier aggregation, the CCs to be used may be set for eachUE.

PCC and SCC

In carrier aggregation, one of the multiple CCs used by a UE is aspecial CC. This special CC is called the primary component carrier(PCC). Also, the remaining CCs among the multiple CCs are calledsecondary component carriers (SCCs). The PCC may be different dependingon the UE. This point will be described more specifically below withreference to FIG. 1.

FIG. 1 is an explanatory diagram for illustrating an example of the PCCsof respective UEs. Referring to FIG. 1, a UE 31A, a UE 31B, and five CCsfrom CC1 to CC5 are illustrated. In this example, the UE 31A is usingthree CCs: CC1, CC2, and CC3. Additionally, the UE 31A is using CC2 asthe PCC. Meanwhile, the UE 31B is using two CCs: CC2 and CC4.Additionally, the UE 31B is using CC4 as the PCC. In this way, each UEmay use a different CC as the PCC.

Since the PCC is the most important CC among the multiple CCs, it isdesirable for the PCC to be the CC with the most stable communicationquality. Note that in actual practice, which CC to treat as the PCCdepends on the implementation.

The SCC is added to the PCC. In addition, an existing SCC that has beenadded may also be removed. Note that changing an SCC is conducted byremoving an existing SCC and adding a new SCC.

PCC Determination Method and Changing Method

When a UE connection is initially established and the status of the UEgoes from Radio Resource Control (RRC) Idle to RRC Connected, the CCthat the UE used during the establishment of the connection becomes thePCC for that UE. More specifically, a connection is established througha connection establishment procedure. At this point, the status of theUE goes from RRC Idle to RRC Connected. Also, the CC used in theprocedure becomes the PCC for the above UE. Note that the aboveprocedure is a procedure initiated from the UE side.

Additionally, PCC changing is conducted by a handover betweenfrequencies. More specifically, if a handover is specified in aconnection reconfiguration procedure, a PCC handover is conducted, andthe PCC is changed. Note that the above procedure is a procedureinitiated from the network side.

Adding SCC

As discussed above, the SCC is added to the PCC. As a result, the SCC isassociated with the PCC. In other words, the SCC is subordinate to thePCC. SSC addition may be conducted through a connection reconfigurationprocedure. Note that this procedure is a procedure initiated from thenetwork side.

Removing SSC

As discussed above, an SCC may be removed. SSC removal may be conductedthrough a connection reconfiguration procedure. Specifically, a specificSCC specified in a message is removed. Note that the above procedure isa procedure initiated from the network side.

In addition, the removal of all SCCs may be conducted through aconnection re-establishment procedure.

Special Role of PCC

The connection establishment procedure, the transmitting and receivingof non-access stratum (NAS) signaling, and the transmitting andreceiving of uplink control signals on the physical uplink controlchannel (PUCCH) are conducted only by the PCC, and not by the SCCs.

In addition, the detection of a radio link failure (RLF) and asubsequent connection re-establishment procedure are also conducted onlyby the PCC, and not by the SCCs. Hereinafter, specific examplesregarding this point will be described with reference to FIGS. 2 and 3.

FIG. 2 is a first explanatory diagram for illustrating an example of aprocedure after the detection of an RLF. Referring to FIG. 2, if the UEdetects a radio link problem (RLP) regarding the PCC after normaloperation, a timer T310 is started. Subsequently, if the timer T310expires, the UE detects an RLF, starts a timer T311, and additionallystarts the connection re-establishment procedure. Subsequently, in theexample illustrated in FIG. 2, the connection re-establishment procedureis successful. Also, the timer T311 stops.

FIG. 3 is a second explanatory diagram for illustrating an example of aprocedure after the detection of a radio link failure (RLF). In theexample illustrated in FIG. 3, the connection re-establishment procedureis unsuccessful. As a result, the timer T311 expires. Subsequently, thestatus of the UE goes from RRC Connected to RRC Idle. Also, if SCCsassociated with the PCC exist, those SCCs are released.

Note that for the SCCs, a procedure like the above is not conducted,even if an RLP is detected.

(Small Cell Anticipated by Release 12)

In Release 12, the investigation of scenarios in which a macro cell eNBand a small cell eNB use separate frequency bands is anticipated. Thispoint will be described more specifically below with reference to FIG.4.

FIG. 4 is an explanatory diagram for illustrating an example of ascenario in which separate frequency bands are used by a macro cell anda small cell. Referring to FIG. 4, a macro cell 10 and a correspondingeNB 11 are illustrated. Also, a small cell 20, which completely overlapswith the macro cell 10, and a corresponding eNB 21 are illustrated.Furthermore, a UE 31 that communicates with the eNB 11 and the eNB 21 isalso illustrated. On such a network, the eNB 11 uses a frequency band inthe 2 GHz band as the frequency band of the macro cell 10, for example,and uses this frequency band to communicate with the UE 31. Meanwhile,the eNB 21 uses a frequency band in the 5 GHz band as the frequency bandof the small cell 20, for example, and uses this frequency band tocommunicate with the UE 31.

In addition, since the macro cell is wide compared to the small cell,scenarios in which the macro cell eNB is responsible for thetransmission of control signals are also being investigated.

(Backhauling Between eNBs)

Backhauling between eNBs is not always ideal. In particular, unlikebackhauling between macro cell eNBs, backhauling between a macro celleNB and a small cell eNB or backhauling between small cell eNBs may notbe ideal. As a result, a delay on the backhaul (for example, a delay ofapproximately 50 ms) may be produced.

Such delays on the backhaul between eNBs may affect wirelesscommunications in the case of carrier aggregation. As a result, there isa possibility of various problems occurring.

Specifically, for example, a UE may use a macro cell CC as the PCC, anduse a small cell CC as a SCC. In this case, an uplink control signal(such as an ACK/NACK, for example) for the SCC may be transmitted by thePCC.

Furthermore, for example, the uplink control signal may be transmittedfrom the eNB of the macro cell to the eNB of the small cell viabackhauling. In such cases, for example, the uplink control signal (suchas an ACK/NACK, for example) may take a large amount of time to reachthe eNB of the small cell because of a delay on the backhaul. As aresult, operation by the eNB of the small cell based on the uplinkcontrol signal may be delayed, and communication quality for the UE maybe lowered.

Note that backhauling between eNBs is logically also called the X2interface. Also, backhauling between eNBs physically includes one ormore physical lines. One example of a physical line is an optical fiberline. The communication speed for backhauling between eNBs depends onthe configuration of that backhaul (such as the type of each physicalline and the number of devices that the data traverses, for example).

(Conditions of Backhauling for Carrier Aggregation)

For example, an acknowledgement (ACK) of a downlink signal on an SCC istransmitted by the PUCCH of the PCC. Since the ACK is used for theretransmission of data by the eNB, a delay of the ACK is not acceptable.Consequently, when a first eNB using a CC that acts as the PCC for a UEis different from a second eNB using a CC that acts as an SCC for theUE, a backhaul delay of approximately 10 ms between the first eNB andthe second eNB is desirable.

2. SCHEMATIC CONFIGURATION OF COMMUNICATION SYSTEM

Next, a schematic configuration of a communication system 1 according toan embodiment of the present disclosure will be described with referenceto FIG. 5. FIG. 5 is an explanatory diagram illustrating an example of aschematic configuration of a communication system 1 according to theembodiment. Referring to FIG. 5, the communication system 1 includes amacro base station 100, a small base station 200, and a terminal device300. Note that the communication system 1 is a communication systemconforming to LTE or LTE-Advanced, for example.

(Macro Base Station 100)

The macro base station 100 wirelessly communicates with the terminaldevice 300 within the macro cell 10. For example, the macro base station100 supports carrier aggregation. In other words, the macro base station100 is able to use multiple component carriers (CCs) simultaneously forwireless communication with one terminal device 300.

As an example, one or more CCs in the 2 MHz band are used as CCs of themacro cell 10. In other words, within the macro cell 10, one or more CCsin the 2 MHz band are used for wireless communication between the macrobase station 100 and the terminal device 300.

(Small Base Station 200)

The small base station 200 wirelessly communicates with the terminaldevice 300 within the small cell 20. The small cell 20 partially orfully overlaps with the macro cell 10. For example, the small basestation 200 also supports carrier aggregation, and is able to usemultiple component carriers (CCs) simultaneously for wirelesscommunication with one terminal device 300.

For example, the small base station 200 uses separate CCs from the CCsused (at least simultaneously) by the macro base station 100. Forexample, the frequency band used within the small cell 20 is a higherfrequency band than the frequency band used within the macro cell 10.

As an example, one or more CCs in the 5 MHz band are used as CCs of thesmall cell 20. In other words, within the small cell 20, one or more CCsin the 5 MHz band are used in wireless communication between the smallbase station 200 and the terminal device 300.

(Terminal Device 300)

The terminal device 300 wirelessly communicates with the macro basestation 100 within the macro cell 10. The terminal device 300 alsowirelessly communicates with the small base station 200 within the smallcell 20.

In addition, the terminal device 300 supports carrier aggregation, andis able to wirelessly communicate using one PCC and one or more SCCs. Asan example, the terminal device 300 wirelessly communicates with themacro base station 100 by using one PCC and one or more SCCs. As anotherexample, the terminal device 300 wirelessly communicates with the smallbase station 200 by using one PCC and one or more SCCs. As yet anotherexample, the terminal device 300 wirelessly communicates with the macrobase station 100 by using one PCC (or one PCC and one or more SCCs),while also wirelessly communicating with the small base station 200 byusing one or more SCCs.

<<Macro Base Station Configuration>>

Next, an example of the configuration of macro base station 100according to the present embodiment will be described with reference toFIGS. 6 to 9. FIG. 6 is a block diagram illustrating an example of theconfiguration of the macro base station 100 according to the presentembodiment. Referring to FIG. 6, the macro base station 100 is equippedwith an antenna unit 110, a radio communication unit 120, a networkcommunication unit 130, a storage unit 140, and a processing unit 150.

(Antenna Unit 110)

The antenna unit 110 emits a signal output by the radio communicationunit 120 into space as a radio wave. Additionally, the antenna unit 110converts a radio wave from space into a signal, and outputs the signalto the radio communication unit 120.

(Radio Communication Unit 120)

The radio communication unit 120 conducts radio communication. Forexample, the radio communication unit 120 transmits a downlink signal tothe terminal device 300 positioned within the macro cell 10, andreceives an uplink signal from the terminal device 300 positioned withinthe macro cell 10. Note that the radio communication unit 120 is able towirelessly communicate on multiple CCs simultaneously.

(Network Communication Unit 130)

The network communication unit 130 communicates with other nodes. Forexample, the network communication unit 130 communicates with the smallbase station 200 via backhauling. Also, the network communication unit130 communicates with a core network node (such as a Mobility ManagementEntity (MME) or a Serving Gateway (S-GW), for example).

(Storage Unit 140)

The storage unit 140 temporarily or permanently stores programs and datafor the operation of the macro base station 100.

(Processing Unit 150)

The processing unit 150 provides various functions of the macro basestation 100. The processing unit 150 includes an information acquisitionunit 151 and a communication control unit 153.

(Information Acquisition Unit 151)

The information acquisition unit 151 acquires information about aterminal device that uses one CC of the macro cell 10 as the PCC.

For example, the storage unit 140 stores information about a terminaldevice that uses one CC of the macro cell 10 as the PCC. Subsequently,the information acquisition unit 151 acquires at least part of thisinformation from the storage unit 140.

For example, the above information about the above terminal deviceincludes identification information for identifying the above terminaldevice. The above information about the above terminal device may alsoinclude capability information for the above terminal device. Thecapability information may include information indicating whether theabove terminal device supports carrier aggregation, for example.

Note that the above terminal device that uses one CC of the macro cell10 as the PCC is the terminal device 300, for example.

(Communication Control Unit 153)

The communication control unit 153 conducts control related to radiocommunication.

(1) Setting CCs to be Used by Terminal Device

For example, the communication control unit 153 sets CCs to be used by aterminal device.

As a specific process, for example, the communication control unit 153sets CCs to be used by a terminal device by updating setting informationabout CCs to be used by the terminal device.

(1-1) Setting PCC to be Used by Terminal Device

The communication control unit 153 sets the PCC to be used by a terminaldevice, for example.

Setting During Connection Establishment

For example, a connection with the terminal device 300 is established ona CC of the macro cell 10. More specifically, for example, the macrobase station 100 and the terminal device 300 conduct the connectionestablishment procedure on one CC of the macro cell 10, and as a result,a connection with the terminal device 300 is established. In this case,the communication control unit 153 sets the above one CC as the PCC tobe used by the terminal device 300.

As an example, setting information indicating a CC of the macro cell 10to be used by a terminal device is stored in the macro base station 100.Subsequently, the communication control unit 153 updates the abovesetting information so that the above setting information indicates thatthe above one CC of the macro cell 10 is the PCC for the terminal device300. As a result, the above one CC is set as the PCC to be used by theterminal device 300. The macro base station 100 then follows the abovesetting information and uses the above one CC as the PCC to wirelesslycommunicate with the terminal device 300.

Setting During Handover

For example, the PCC to be used by the terminal device 300 is changedfrom a first CC of the macro cell 10 to a second CC of the macro cell 10by a handover. In this case, the communication control unit 153 sets theabove second CC as the PCC to be used by the terminal device 300.

As an example, the communication control unit 153 updates the abovesetting information so that the above setting information indicates thatthe above second CC of the macro cell 10 is the PCC for the terminaldevice 300. As a result, the above second CC is set as the PCC to beused by the terminal device 300. The macro base station 100 then followsthe above setting information and uses the above second CC as the PCC towirelessly communicate with the terminal device 300.

(1-2) Setting Additional CC to be Used by Terminal Device

The communication control unit 153 sets an additional CC to be used by aterminal device.

For example, the communication control unit 153 sets one or more CCs ofthe small cell 20 as additional CCs to be used additionally by aterminal device using one CC of the macro cell 10 as the PCC.

Setting Sub PCC

Particularly, in the present embodiment, the communication control unit153, for example, sets one CC among the above one or more CCs of thesmall cell 20 as a special CC by which the above terminal device (thatis, the terminal device using one CC of the macro cell 10 as the PCC) isable to transmit uplink control information on an uplink controlchannel. In this specification, this special CC is called the “sub PCC”.It should be understood that this special CC may also be called othernames instead of sub PCC, such as small PCC or super SCC. Hereinafter, aspecific example of setting the sub PCC will be described with referenceto FIG. 7.

FIG. 7 is an explanatory diagram for illustrating an example of settingthe sub PCC. Referring to FIG. 7, CC1 and CC2 used by the macro basestation 100 as well as CC3, CC4, and CC5 used by the small base station200 are illustrated. For example, when the terminal device 300 uses thefive CCs from CC1 to CC5, the communication control unit 153 sets CC1 asthe PCC for the terminal device 300, and sets CC4 as the sub PCC for theterminal device 300.

Characteristics of Sub PCC

As discussed above, the sub PCC is a CC of the small cell 20.Furthermore, the sub PCC is a CC by which the above terminal device(that is, the terminal device using one CC of the macro cell 10 as thePCC) is able to transmit uplink control information on an uplink controlchannel.

The above uplink control channel is the physical uplink control channel(PUCCH), for example. In other words, the sub PCC is a CC by which theabove terminal device is able to transmit uplink control information bythe PUCCH.

The above uplink control information includes, for example, anacknowledgement (ACK) and a negative acknowledgement (NACK) regardingthe reception of a downlink signal. In other words, the sub PCC is a CCby which an ACK/NACK may be transmitted on an uplink control channel(for example, the PUCCH). As an example, this ACK/NACK is a hybridautomatic repeat request (HARQ) ACK/NACK.

Additionally, the above uplink control information includes, forexample, a scheduling request (SR). In other words, the sub PCC is a CCby which a scheduling request (SR) may be transmitted on an uplinkcontrol channel (for example, the PUCCH).

Additionally, the above uplink control information includes, forexample, periodically reported channel state information (CSI). In otherwords, the sub PCC is a CC by which a periodically reported CSI may betransmitted on an uplink control channel (for example, the PUCCH). Notethat the CSI includes information such as a channel quality indicator(CQI), a precoding matrix indicator (PMI), a precoding type indicator(PTI), and/or a rank indicator (RI), for example.

Additionally, the above uplink control information may also includeinformation for power control. In other words, the sub PCC may be a CCby which information for power control may be transmitted on an uplinkcontrol channel (for example, the PUCCH).

By setting the sub PCC as above, it becomes possible to reduce theeffect of backhauling on wireless communications in the case of carrieraggregation.

More specifically, ordinarily uplink control information on an uplinkcontrol channel (PUCCH) is not transmitted by an SCC, and instead,uplink control information for an SCC is transmitted on an uplinkcontrol channel (PUCCH) of the PCC. For this reason, if the SCC is a CCof the small cell 20 and the PCC is a CC of the macro cell 10, a delayon the backhaul may cause uplink control information for an SCC to takea long time to reach the small base station 200. Accordingly, asdiscussed above, one CC of the small cell 20 is set as the sub PCC.Uplink control information is then transmitted on the uplink controlchannel (PUCCH) of the sub PCC. Consequently, the effect of backhaulingon wireless communications is reduced, for example.

As another example, since an ACK/NACK is transmitted on the uplinkcontrol channel (PUCCH) of the sub PCC, the ACK/NACK reaches the smallbase station 200 rapidly. Consequently, suitable retransmission controlmay be possible.

As another example, since a scheduling request is transmitted on theuplink control channel (PUCCH) of the sub PCC, the scheduling requestreaches the small base station 200 quickly. Consequently, rapidscheduling may be possible.

As another example, since periodically reported CSI is transmitted onthe uplink control channel (PUCCH) of the sub PCC, the CSI reaches thesmall base station 200 quickly. Consequently, rapid adaptation of thewireless communications of the above terminal device to the environmentmay be possible.

Note that, as discussed above, the connection establishment procedure isconducted on the PCC. For this reason, the sub PCC for a terminal deviceis a CC that is not used by that terminal device to conduct theconnection establishment procedure. Also, for example, the sub PCC for aterminal device is a CC that is not used to conduct NAS signaling tothat terminal device.

Also, for example, the sub PCC is a CC selected for each terminaldevice. In other words, if the sub PCC of a certain terminal device is afirst CC of the small cell 20, the sub PCC of another terminal devicemay be a second CC of the small cell 20.

Conditions of Setting

For example, if the backhaul between the macro base station 100 and thesmall base station 200 does not satisfy a prescribed quality standard,the communication control unit 153 sets the above one CC among the aboveone or more CCs of the small cell 20 as the sub PCC.

Specifically, for example, backhaul information indicating whether ornot the backhaul between the macro base station 100 and the small basestation 200 satisfies the above prescribed quality standard is stored inthe storage unit 140. In other words, this backhaul information isinformation indicating whether or not the above backhaul is ideal. Fromthe above backhaul information, the communication control unit 153checks whether or not the above backhaul satisfies the above prescribedquality standard (that is, whether or not the above backhaul is ideal).Subsequently, if the above backhaul does not satisfy the aboveprescribed quality standard, the communication control unit 153 sets oneCC of the small base station 200 as the sub PCC. Note that the abovebackhaul information may be predetermined information, or informationthat is changed dynamically according to the communication conditions onthe backhaul.

Consequently, it becomes possible to set the sub PCC in cases where thedelay on the backhaul may become large, for example.

As an example, the above prescribed quality standard includes standardsfor communication speed, throughput, and/or latency. Obviously, theabove prescribed quality standard may also include other standards ofquality in addition to, or instead of, these standards.

Specific Setting Method

For example, on the basis of a result of measurement by the terminaldevice 300 (for example, a measurement report), one CC of the small cell20 is determined as an additional CC to be used by the terminal device300. In this case, if the backhaul between the macro base station 100and the small base station 200 does not satisfy the above prescribedquality standard, and in addition, the sub PCC of the terminal device300 does not yet exist, the communication control unit 153 sets theabove one CC of the small base station 200 as the sub PCC.

As an example, setting information indicating a CC of the small cell 20to be used by a terminal device is stored in the small base station 200.Subsequently, the communication control unit 153 causes the small basestation 200 to update the above setting information so that the abovesetting information indicates that the above one CC of the small cell 20is the sub PCC for the terminal device 300. As an example, thecommunication control unit 153 provides a message with instructions toupdate the above setting information to the small base station 200 viathe network communication unit 130, and thereby causes the small basestation 200 to update the above setting information. As a result, theabove one CC is set as the sub PCC to be used by the terminal device300. The small base station 200 then follows the above settinginformation and uses the above one CC as the sub PCC to wirelesslycommunicate with the terminal device 300.

Setting SCC Associated with Sub PCC

For example, the communication control unit 153 sets a CC not set as thesub PCC from among the above one or more CCs of the small cell 20 (thatis, the one or more CCs set as the above additional CCs) as an SCCassociated with the sub PCC. For example, the communication control unit153 sets each of the remaining CCs other than the sub PCC from among theabove one or more CCs of the small cell 20 as an SCC associated with thesub PCC. Hereinafter, a specific example of setting SCCs associated withthe sub PCC will be described with reference to FIG. 8.

FIG. 8 is an explanatory diagram for illustrating an example of settingSCCs associated with the sub PCC. Referring to FIG. 8, CC1 and CC2 usedby the macro base station 100 as well as CC3, CC4, and CC5 used by thesmall base station 200 are illustrated. For example, the terminal device300 uses the five CCs from CC1 to CC5. In this example, thecommunication control unit 153 sets CC1 as the PCC for the terminaldevice 300, and sets CC2 as an SCC associated with the PCC. In addition,the communication control unit 153 sets CC4 as the sub PCC for theterminal device 300, and sets each of CC3 and CC5 as an SCC associatedwith the sub PCC.

Characteristics of SCC Associated with Sub PCC

An SCC associated with the sub PCC is a CC by which a terminal device isunable to transmit the above uplink control information on the aboveuplink control channel. More specifically, for example, the above SCCassociated with the sub PCC is a CC by which the above terminal deviceis unable to transmit information such as an ACK/NACK, a schedulingrequest, and/or CSI on the PUCCH.

In addition, the above uplink control information for an SCC associatedwith the sub PCC is transmitted on the above uplink control channel ofthe sub PCC. More specifically, for example, information such as anACK/NACK, a scheduling request, and/or CSI for an SCC associated withthe sub PCC is transmitted on the PUCCH of the sub PCC.

Consequently, for example, not only uplink control information for thesub PCC but also uplink control information for an SCC associated withthe sub PCC may be transmitted on the uplink control channel (PUCCH) ofthe sub PCC. Consequently, the effect of backhauling on wirelesscommunications is reduced further, for example.

Conditions of Setting

The conditions of setting an SCC associated with the sub PCC are thesame as the conditions of setting the sub PCC discussed above. In otherwords, if the backhaul between the macro base station 100 and the smallbase station 200 does not satisfy a prescribed quality standard, thecommunication control unit 153 sets a CC not set as the sub PCC fromamong the above one or more CCs of the small cell 20 as an SCCassociated with the sub PCC.

Specific Setting Method

For example, on the basis of a result of measurement by the terminaldevice 300 (for example, a measurement report), one CC of the small cell20 is determined as an additional CC to be used by the terminal device300. In this case, if the backhaul between the macro base station 100and the small base station 200 does not satisfy the above prescribedquality standard, and in addition, the sub PCC of the terminal device300 already exists, the communication control unit 153 sets the aboveone CC of the small base station 200 as an SCC associated with the subPCC.

As an example, setting information indicating a CC of the small cell 20to be used by a terminal device is stored in the small base station 200.Subsequently, the communication control unit 153 causes the small basestation 200 to update the above setting information so that the abovesetting information indicates that the above one CC of the small cell 20is an SCC associated with the sub PCC. As an example, the communicationcontrol unit 153 provides a message with instructions to update theabove setting information to the small base station 200 via the networkcommunication unit 130, and thereby causes the small base station 200 toupdate the above setting information. As a result, the above one CC isset as an SCC associated with the sub PCC. The small base station 200then follows the above setting information and uses the above one CC asan SCC associated with the sub PCC to wirelessly communicate with theterminal device 300.

Setting SCC Associated with PCC

The communication control unit 153 may set each of the above one or moreCCs of the small cell 20 (that is, the one or more CCs set as the aboveadditional CCs) as an SCC associated with the PCC. Hereinafter, aspecific example of setting an SCC associated with the PCC will bedescribed with reference to FIG. 9.

FIG. 9 is an explanatory diagram for illustrating an example of settingan SCC associated with the PCC. Referring to FIG. 9, CC1 and CC2 used bythe macro base station 100 as well as CC3, CC4, and CC5 used by thesmall base station 200 are illustrated. For example, the terminal device300 uses the five CCs from CC1 to CC5. In this example, thecommunication control unit 153 sets CC1 as the PCC for the terminaldevice 300, and sets CC2 to CC5 as SCCs associated with the PCC.

Conditions of Setting

For example, if the backhaul between the macro base station 100 and thesmall base station 200 satisfies a prescribed quality standard, thecommunication control unit 153 sets each of the above one or more CCs ofthe small cell 20 as an SCC associated with the PCC.

Specifically, for example, as discussed above, the above backhaulinformation (that is, information indicating whether or not the backhaulbetween the macro base station 100 and the small base station 200satisfies the above prescribed quality standard) is stored in thestorage unit 140. From the above backhaul information, the communicationcontrol unit 153 checks whether or not the above backhaul satisfies theabove prescribed quality standard (that is, whether or not the abovebackhaul is ideal). Subsequently, if the above backhaul satisfies theabove prescribed quality standard, the communication control unit 153sets CCs of the small base station 200 as SCCs associated with the PCC.

Consequently, for example, if a small delay on the backhaul isanticipated, it becomes possible to treat the CCs of the small cell asSCCs associated with the PCC. For this reason, the small base station200 may be dedicated to transmitting and receiving data, for example. Asa result, throughput in the small cell 20 may be improved.

Specific Setting Method

For example, on the basis of a result of measurement by the terminaldevice 300 (for example, a measurement report), one CC of the small cell20 is determined as an additional CC to be used by the terminal device300. In this case, if the backhaul between the macro base station 100and the small base station 200 satisfies the above prescribed qualitystandard, the communication control unit 153 sets the above one CC ofthe small cell 20 as an SCC associated with the PCC (a CC of the macrocell 10).

As an example, setting information indicating a CC of the small cell 20to be used by a terminal device is stored in the small base station 200.Subsequently, the communication control unit 153 causes the small basestation 200 to update the above setting information so that the abovesetting information indicates that the above one CC of the small cell 20is an SCC associated with the PCC (a CC of the macro cell 10). As anexample, the communication control unit 153 provides a message withinstructions to update the above setting information to the small basestation 200 via the network communication unit 130, and thereby causesthe small base station 200 to update the above setting information. As aresult, the above one CC is set as an SCC associated with the PCC (a CCof the macro cell 10). The small base station 200 then follows the abovesetting information and uses the above one CC as an SCC associated withthe PCC to wirelessly communicate with the terminal device 300.

As above, a CC of the small cell 10 is set as an additional CC to beused by a terminal device that uses one CC of the macro cell 10 as thePCC. More specifically, the relevant CC of the small cell 10 is set asthe sub PCC, an SCC associated with the sub PCC, or an SCC associatedwith the PCC.

(2) Notification to Terminal Device

When setting a CC as an additional CC to be used by a terminal device,for example, the communication control unit 153 notifies the relevantterminal device that the relevant CC is added.

For example, when setting a CC of the small cell 20 as an additional CCto be used by a terminal device, the communication control unit 153notifies the relevant terminal device that the relevant CC of the smallcell 20 is added.

Notification of Addition of Sub PCC

For example, when newly setting a CC of the small cell 20 as anadditional CC to be used by a terminal device, if the relevant CC is setas the sub PCC, the communication control unit 153 notifies the aboveterminal device that the relevant CC is added as the sub PCC.

More specifically, for example, the communication control unit 153notifies the above terminal device that the above CC is added as the subPCC in a message during the connection reconfiguration procedure. Therelevant message includes information for specifying the above CC andinformation indicating that the above CC is the sub PCC, for example.Also, as an example, the above message is a message with a command foradding a secondary cell as the sub PCC.

According to such a notification, for example, a terminal device using aCC of the macro cell 10 as the PCC becomes able to learn which CC is thesub PCC for the relevant terminal device. For this reason, the relevantterminal device becomes able to actually transmit uplink controlinformation on the uplink control channel of the sub PCC. Note thatsince the terminal device conducts procedures such as the connectionestablishment procedure on the PCC, the PCC is self-evident to theterminal device, but since the terminal device does not conductprocedures such as the connection establishment procedure on the subPCC, the sub PCC is not self-evident to the terminal device. For thisreason, a notification like the above is particularly effective.

Notification of Addition of SCC Associated with Sub PCC

For example, when newly setting a CC of the small cell 20 as anadditional CC to be used by a terminal device, if the relevant CC is setas an SCC associated with the sub PCC, the communication control unit153 notifies the above terminal device that the relevant CC is added asan SCC associated with the sub PCC.

More specifically, for example, the communication control unit 153notifies the above terminal device that the above CC is added as an SCCassociated with the sub PCC in a message during the connectionreconfiguration procedure. The relevant message includes information forspecifying the above CC and information indicating that the above CC isan SCC associated with the sub PCC, for example. Also, as an example,the above message is a message with a command for adding a secondarycell as an SCC associated with the sub PCC.

According to such a notification, for example, a terminal device using aCC of the macro cell 10 as the PCC becomes able to learn which CC is anSCC associated with the sub PCC. For this reason, the relevant terminaldevice becomes able to actually transmit uplink control information forthe relevant SCC on the uplink control channel of the sub PCC.

Notification of Addition of SCC Associated with PCC

For example, when newly setting a CC of the small cell 20 as anadditional CC to be used by a terminal device, if the relevant CC is setas an SCC associated with the PCC, the communication control unit 153notifies the above terminal device that the relevant CC is added as anSCC.

As an example, the communication control unit 153 simply notifies theabove terminal device that the above CC is added as an SCC in a messageduring the connection reconfiguration procedure. The relevant messageincludes information for specifying the above CC, for example. Also, asan example, the above message is a message with a command for adding asecondary cell.

4. TERMINAL DEVICE CONFIGURATION

Next, FIG. 10 will be referenced to describe an example of aconfiguration of the terminal device 300 according to the presentembodiment. FIG. 10 is a block diagram illustrating an example of aconfiguration of the terminal device 300 according to the presentembodiment. Referring to FIG. 10, the terminal device 300 is equippedwith an antenna unit 310, a radio communication unit 320, a storage unit330, an input unit 340, a display unit 350, and a processing unit 360.

(Antenna Unit 310)

The antenna unit 310 emits a signal output by the radio communicationunit 320 into space as a radio wave. Additionally, the antenna unit 310converts a radio wave from space into a signal, and outputs the signalto the radio communication unit 320.

(Radio Communication Unit 320)

The radio communication unit 320 conducts radio communication. Forexample, if the terminal device 300 is positioned inside the macro cell10, the radio communication unit 320 receives a downlink signal from themacro base station 100, and transmits an uplink signal to the macro basestation 100. As another example, if the terminal device 300 ispositioned inside the small cell 20, the radio communication unit 320receives a downlink signal from the small base station 200, andtransmits an uplink signal to the small base station 200.

(Storage Unit 330)

The storage unit 330 temporarily or permanently stores programs and datafor the operation of the terminal device 300.

(Input Unit 340)

The input unit 340 receives input from a user of the terminal device300. The input unit 340 then provides an input result to the processingunit 360.

(Display Unit 350)

The display unit 350 displays an output screen (that is, an outputimage) from the terminal device 300. For example, the display unit 350displays an output screen according to control by the processing unit360 (display control unit 365).

(Information Acquisition Unit 351)

The information acquisition unit 351 acquires information about anadditional CC to be used additionally by the terminal device 300.

For example, the above information about the above additional CCincludes information for specifying the relevant additional CC. As anexample, the relevant information for specifying the above additional CCis identification information for identifying the above additional CC.

As a specific example, if a CC of the small cell 20 is set as anadditional CC to be used additionally by the terminal device 300, theterminal device 300 is notified of the addition of the above CC of thesmall cell 20. As an example, the terminal device 300 is notified of theaddition of the above CC of the small cell 20 in a message during theconnection reconfiguration procedure. This message includes informationfor specifying the above CC, and this information is stored in thestorage unit 330. Subsequently, the information acquisition unit 351acquires information for specifying the above CC from the storage unit330, for example.

Note that, as a first example, when the above CC is added as the subPCC, the above message additionally includes information indicating thatthe above CC is the sub PCC. In this case, information for specifyingthe above CC is stored in the storage unit 330 as information forspecifying the sub PCC. As a second example, when the above CC is addedas an SCC associated with the sub PCC, the above message additionallyincludes information indicating that the above CC is an SCC associatedwith the sub PCC. In this case, information for specifying the above CCis stored in the storage unit 330 as information for specifying an SCCassociated with the sub PCC. As a third example, when the above CC isadded as an SCC associated with the PCC, the above message does notinclude additional information as discussed above. In this case,information for specifying the above CC is stored in the storage unit330 as information for specifying an SCC associated with the PCC.

Case of Sub PCC

For example, the terminal device 300 uses one CC of the macro cell 10 asthe PCC. Also, one or more CCs of the small cell 20 are set asadditional CCs to be used additionally by the terminal device 300, andone CC among these one or more CCs is set as the sub PCC. In this case,the information acquisition unit 351 acquires information about therelevant one CC (that is, the sub PCC).

Case of SCC Associated with Sub PCC

For example, the terminal device 300 uses one CC of the macro cell 10 asthe PCC. Also, one or more CCs of the small cell 20 are set asadditional CCs to be used additionally by the terminal device 300, andone CC not set as the sub PCC from among these one or more CCs is set asan SCC associated with the sub PCC. In this case, the informationacquisition unit 351 acquires information about the relevant one CC setas an SCC associated with the sub PCC.

Case of SCC Associated with PCC

For example, the terminal device 300 uses one CC of the macro cell 10 asthe PCC. Also, each of one or more CCs of the small cell 20 is set as anadditional CC to be used additionally by the terminal device 300, andmore specifically, may be set as an SCC associated with the PCC. In thiscase, the information acquisition unit 351 acquires information aboutthe above one or more CCs respectively set as an SCC associated with thePCC.

(Communication Control Unit 363)

The communication control unit 363 conducts control related to wirelesscommunication by the terminal device 300.

For example, the communication control unit 363 controls wirelesscommunication by the terminal device 300 so that uplink controlinformation is transmitted on an uplink control channel.

Transmission on Uplink Control Channel of Sub PCC

Particularly, in the present embodiment, the communication control unit363 controls wireless communication on one CC set as the sub PCC so thatuplink control information is transmitted on the uplink control channelof the above one CC.

As discussed above, the above uplink control channel is the PUCCH, forexample. Also, the above uplink control information includes informationsuch as an ACK/NACK, a scheduling request, and/or periodically reportedCSI. In other words, for example, the communication control unit 363controls wireless communication on one CC set as the sub PCC so thatinformation such as an ACK/NACK, a scheduling request, and/orperiodically reported CSI is transmitted on the PUCCH of the above oneCC.

Specifically, for example, the communication control unit 363 maps asignal of the above uplink control information to a radio resource forthe above uplink control channel (PUCCH) of the above one CC set as thesub PCC. Consequently, the above uplink control information istransmitted on the above uplink control channel (PUCCH).

Note that the communication control unit 363 controls wirelesscommunication on the sub PCC so that not only uplink control informationfor the sub PCC but also uplink control information for an SCCassociated with the sub PCC is transmitted on the uplink control channelof the sub PCC.

Transmission on Uplink Control Channel of PCC

For example, the communication control unit 363 controls wirelesscommunication on one CC set as the PCC so that uplink controlinformation is transmitted on the uplink control channel of the aboveone CC. The above one CC set as the PCC is a CC of the macro cell 10,for example.

For example, the communication control unit 363 controls wirelesscommunication on one CC set as the PCC so that information such as anACK/NACK, a scheduling request, and/or periodically reported CSI istransmitted on the PUCCH of the above one CC.

Specifically, for example, the communication control unit 363 maps asignal of the above uplink control information to a radio resource forthe above uplink control channel (PUCCH) of the above one CC set as thePCC. Consequently, the above uplink control information is transmittedon the above uplink control channel (PUCCH).

Note that the communication control unit 363 controls wirelesscommunication on the PCC so that not only uplink control information forthe PCC but also uplink control information for an SCC associated withthe PCC is transmitted on the uplink control channel of the PCC.

(Display Control Unit 365)

The display control unit 365 controls the display of an output screen bythe display unit 350. For example, the display control unit 365generates an output screen to be displayed by the display unit 350, andcauses the display unit 350 to display that output screen.

5. Process Flow

Next, FIGS. 11 to 14 will be referenced to describe an example of aprocess according to the present embodiment.

(Process Related to Setting Additional CC)

FIG. 11 is a flowchart illustrating an example of a diagrammatic flow ofa process related to setting an additional CC according to the presentembodiment. Note that this process is executed after a CC of the macrocell 10 is decided as the PCC and a CC of the small cell 20 is decidedas an additional CC to be used additionally by the terminal device 300.

First, if the backhaul between the macro base station 100 and the smallbase station 200 satisfies a prescribed quality standard (S401: YES),the communication control unit 153 newly sets a CC of the small cell 20as an SCC associated with the PCC (a CC of the macro cell 10) (S403).The process then ends.

If the above backhaul does not satisfy the above prescribed qualitystandard (S401: NO), and if another CC of the small cell 20 is alreadyset as the sub PCC for the terminal device 300 (S405: YES), thecommunication control unit 153 newly sets a CC of the small cell 20 asan SCC associated with the sub PCC (S407). The process then ends.

If no CC of the small cell 20 has been set as the sub PCC for theterminal device 300 (S405: NO), the communication control unit 153 newlysets a CC of the small cell 20 as the sub PCC (S409). The process thenends.

(Connection Reconfiguration Procedure: SCC Associated with PCC)

FIG. 12 is a flowchart illustrating a first example of a diagrammaticflow of a connection reconfiguration procedure according to the presentembodiment. The first example is an example for a case in which a CC ofthe small cell 20 is newly set as an SCC associated with the PCC like instep S403 illustrated in FIG. 11.

First, the macro base station 100 transmits, in the PCC (a CC of themacro cell 10) for the terminal device 300, an RRC ConnectionReconfiguration message with a command for adding a secondary cell tothe terminal device 300 (S421).

Subsequently, after connection reconfiguration is completed, theterminal device 300 transmits, in the PCC for the terminal device 300,an RRC Connection Reconfiguration Complete message to the macro basestation 100 (S423). The procedure then ends.

(Connection Reconfiguration Procedure: Sub PCC)

FIG. 13 is a flowchart illustrating a second example of a diagrammaticflow of a connection reconfiguration procedure according to the presentembodiment. The second example is an example for a case in which a CC ofthe small cell 20 is newly set as the sub PCC like in step S409illustrated in FIG. 11.

First, the macro base station 100 transmits, in the PCC (a CC of themacro cell 10) for the terminal device 300, an RRC ConnectionReconfiguration message with a command for adding a secondary cell asthe sub PCC to the terminal device 300 (S431).

Subsequently, after connection reconfiguration is completed, theterminal device 300 transmits, in the PCC for the terminal device 300,an RRC Connection Reconfiguration Complete message to the macro basestation 100 (S433). The procedure then ends.

(Connection Reconfiguration Procedure: SCC Associated with Sub PCC)

FIG. 14 is a flowchart illustrating a third example of a diagrammaticflow of a connection reconfiguration procedure according to the presentembodiment. The third example is an example for a case in which a CC ofthe small cell 20 is newly set as an SCC associated with the sub PCClike in step S407 illustrated in FIG. 11.

First, the macro base station 100 transmits, in the PCC (a CC of themacro cell 10) for the terminal device 300, an RRC ConnectionReconfiguration message with a command for adding a secondary cell as anSCC associated with the sub PCC to the terminal device 300 (S441).

Subsequently, after connection reconfiguration is completed, theterminal device 300 transmits, in the PCC for the terminal device 300,an RRC Connection Reconfiguration Complete message to the macro basestation 100 (S433). The procedure then ends.

6. MODIFICATIONS

Next, modifications of the present embodiment will be described withreference to FIGS. 15 to 21.

<6.1. First Modification>

First, a first modification of the present embodiment will be describedwith reference to FIGS. 15 and 16.

According to the first modification of the present embodiment, one CCset as an SCC associated with the sub PCC is newly set as the sub PCC,thereby changing the sub PCC. Consequently, it becomes possible toupdate the sub PCC with a reduced burden, for example.

(Macro Base Station 100: Communication Control Unit 153)

(1-2) Setting Additional CC to be Used by Terminal Device

Setting Sub PCC

In the first modification of the present embodiment, the communicationcontrol unit 153 changes the sub PCC by newly setting, as the sub PCC,one CC currently set as an SCC associated with the sub PCC.

For example, the changing of the sub PCC from a first CC currently setas the sub PCC to a second CC currently set as an SCC associated withthe sub PCC is decided on the basis of a result of measurement by theterminal device 300 (for example, a measurement report). Subsequently,the communication control unit 153 sets the above second CC as the subPCC.

As an example, setting information indicating a CC of the small cell 20to be used by a terminal device is stored in the small base station 200.Subsequently, the communication control unit 153 causes the small basestation 200 to update the above setting information so that the abovesetting information indicates that the above second CC of the small cell20 is the sub PCC for the terminal device 300. As a result, the abovesecond CC is set as the sub PCC to be used by the terminal device 300.The small base station 200 then follows the above setting informationand uses the above second CC as the sub PCC to wirelessly communicatewith the terminal device 300. In this way, the sub PCC is changed fromthe above first CC to the above second CC.

Consequently, for example, changing the sub PCC does not require acomplicated procedure like a handover, unlike changing the PCC. For thisreason, the sub PCC may be changed with a reduced burden, for example.

Note that the above first CC that was set as the sub PCC may be set asan SCC associated with the changed sub PCC (that is, the above secondCC), or removed from the additional CCs used by the terminal device 300.

Association with Sub PCC after Change of Sub PCC

For example, after the change of the sub PCC, another CC set as an SCCassociated with the sub PCC is associated with the above one CC newlyset as the sub PCC. Hereinafter, a specific example regarding this pointwill be described with reference to FIG. 15.

FIG. 15 is an explanatory diagram for illustrating an example ofchanging a sub PCC and associating an SCC. Referring to FIG. 15, forexample, before the change of the sub PCC, CC4 is the sub PCC for theterminal device 300, and each of CC3 and CC5 is an SCC associated withthe sub PCC. After that, the sub PCC is changed, and CC3 becomes the subPCC for the terminal device 300, while each of CC4 and CC5 becomes anSCC associated with the sub PCC. In this way, before the change of thesub PCC, CC5 is associated with CC4 which acts as the sub PCC at thattime, but after the change of the sub PCC, CC5 is associated with CC3which acts as the sub PCC at that time.

Consequently, for example, even if the sub PCC is changed, an SCCassociated with the sub PCC is not deactivated, but instead continues tobe used. For this reason, re-adding a CC is not necessary, and thus theburden may be reduced. In other words, the sub PCC may be changed with areduced burden.

Note that, for example, if two or more CCs of the small cell 20 areadditional CCs to be used by the terminal device 300, and one CC of thetwo or more CCs is the sub PCC, the remaining CCs among the above two ormore CCs are SCCs associated with the sub PCC. Thus, the target ofassociation for a CC (for example, CC5 in FIG. 15) may be changedwithout conducting some kind of process in particular. However, ifassociation information indicating the target of association for a CCexists, obviously the target of association for a CC (for example, CC5in FIG. 15) may be changed by updating the association information. Therelevant association information may be information that is part of theabove setting information, or information that is separate from theabove setting information.

(2) Notification to Terminal Device

Notification of Change of Sub PCC

For example, during the change of the sub PCC, the communication controlunit 153 notifies the above terminal device that the sub PCC is changedto the above one CC newly set as the sub PCC.

More specifically, for example, the communication control unit 153notifies the above terminal device that the sub PCC is changed to theabove one CC newly set as the sub PCC in a message during the connectionreconfiguration procedure. The relevant message includes information forspecifying the CC to act as the sub PCC after the change and informationindicating that the sub PCC is changed to the relevant CC, for example.As an example, the above message is a message with a command forchanging the sub PCC.

According to such a notification, for example, a terminal device using aCC of the macro cell 10 as the PCC becomes able to learn of the changeof the sub PCC. For this reason, the relevant terminal device becomesable to actually transmit uplink control information on the uplinkcontrol channel of the sub PCC after the change of the sub PCC.

(Terminal Device 300: Communication Control Unit 363)

In the first embodiment of the present embodiment, the sub PCC ischanged as discussed above. In other words, one CC currently set as anSCC associated with the sub PCC is newly set as the sub PCC. In thiscase, the communication control unit 363 controls wireless communicationon the above one CC newly set as the sub PCC so that uplink controlinformation is transmitted on the uplink control channel of the aboveone CC.

(Process Flow: Connection Reconfiguration Procedure)

FIG. 16 is a flowchart illustrating an example of a diagrammatic flow ofa connection reconfiguration procedure according to the firstmodification of the present embodiment. This procedure is the procedurefor the case in which the sub PCC is changed.

First, the macro base station 100 transmits, in the PCC (a CC of themacro cell 10) for the terminal device 300, an RRC ConnectionReconfiguration message with a command for changing the sub PCC to theterminal device 300 (S451).

Subsequently, after connection reconfiguration is completed, theterminal device 300 transmits, in the PCC for the terminal device 300,an RRC Connection Reconfiguration Complete message to the macro basestation 100 (S453). The procedure then ends.

<6.2. Second Modification>

Next, a second modification of the present embodiment will be describedwith reference to FIGS. 17 to 21.

According to the second modification of the present embodiment, if aradio link failure (RLF) occurs on the sub PCC, one CC currently set asan SCC associated with the sub PCC is newly set as the sub PCC via aprescribed procedure. Consequently, for example, even if an RLF occurson the sub PCC and the sub PCC becomes unusable, an SCC that wasassociated with the sub PCC may continue to be used. For this reason,communication quality may be improved, for example.

(Macro Base Station 100: Communication Control Unit 153)

(1-2) Setting Additional CC to be Used by Terminal Device

Setting Sub PCC

In the second modification of the present embodiment, if a radio linkfailure (RLF) occurs on the sub PCC, the communication control unit 153newly sets one CC currently set as an SCC associated with the sub PCC asthe sub PCC via a prescribed procedure. In other words, when an RLFoccurs on the sub PCC, the communication control unit 153 changes thesub PCC.

The above prescribed procedure is, for example, the connectionreconfiguration procedure for changing the sub PCC. Hereinafter, FIG. 17will be referenced to describe a series of operations related to theoccurrence of an RLF.

FIG. 17 is an explanatory diagram for illustrating a first example of aseries of operations related to the occurrence of a radio link failure(RLF). Referring to FIG. 17, if the terminal device 300 detects a radiolink problem (RLP) regarding the sub PCC after normal operation, a timer1 is started. Subsequently, if the timer 1 expires, the terminal device300 detects an RLF, and starts a timer T2. Also, the terminal device 300notifies the macro base station 100 of the expiration of the timer 1 byRRC signaling. Subsequently, the macro base station 100 transmits an RRCConnection Reconfiguration message with a command for changing the subPCC to the terminal device 300. Subsequently, in the example illustratedin FIG. 17, the connection reconfiguration procedure is successful, andthe sub PCC is changed successfully. Also, the timer 2 stops.

Consequently, for example, even if an RLF occurs on the sub PCC and thesub PCC becomes unusable, an SCC that was associated with the sub PCCmay continue to be used. For this reason, communication quality may beimproved, for example.

On the other hand, for example, if the above prescribed procedure doesnot complete within a prescribed period, the communication control unit153 stops usage of the sub PCC and the SCC associated with the sub PCCby the above terminal device. For example, the sub PCC and the SCCassociated with the sub PCC are deactivated. Hereinafter, a specificexample regarding this point will be described with reference to FIG.18.

FIG. 18 is an explanatory diagram for illustrating a second example of aseries of operations related to the occurrence of a radio link failure(RLF). In the example illustrated in FIG. 18, unlike the exampleillustrated in FIG. 17, the timer 2 expires before the RRC ConnectionReconfiguration procedure succeeds. In this case, the communicationcontrol unit 153 deactivates the sub PCC and the SCC associated with thesub PCC.

Consequently, for example, even though communication on the sub PCC isdifficult, continued usage of the sub PCC may be avoided. As anotherexample, even though transmitting uplink control information for an SCCassociated with the sub PCC (such as an ACK/NACK, a scheduling request,and periodically reported CSI) is difficult, continued usage of theabove SCC may be avoided. As a result, wireless communicationsassociated with degraded communication quality may be stopped rapidly.

Note that the above prescribed procedure may also be a connectionre-establishment procedure for changing the sub PCC, for example.Hereinafter, specific examples regarding this point will be describedwith reference to FIGS. 19 and 20.

FIG. 19 is an explanatory diagram for illustrating a third example of aseries of operations related to the occurrence of a radio link failure(RLF). Referring to FIG. 19, if the terminal device 300 detects a radiolink problem (RLP) regarding the sub PCC after normal operation, a timer1 is started. Subsequently, if the timer 1 expires, the terminal device300 detects an RLF, and starts a timer T2. Also, the terminal device 300transmits an RRC Connection Re-establishment Request with a request tochange the sub PCC to the macro base station 100. Subsequently, in theexample illustrated in FIG. 19, the connection re-establishmentprocedure is successful, and the sub PCC is changed successfully. Also,the timer 2 stops.

FIG. 20 is an explanatory diagram for illustrating a fourth example of aseries of operations related to the occurrence of a radio link failure(RLF). In the example illustrated in FIG. 20, unlike the exampleillustrated in FIG. 19, the timer 2 expires before the RRC ConnectionRe-establishment procedure succeeds. In this case, the communicationcontrol unit 153 deactivates the sub PCC and the SCC associated with thesub PCC.

(Terminal Device 300: Communication Control Unit 363)

In the second embodiment of the present embodiment, the sub PCC ischanged in response to the occurrence of an RLF as discussed above. Inother words, one CC currently set as an SCC associated with the sub PCCis newly set as the sub PCC. In this case, the communication controlunit 363 controls wireless communication on the above one CC newly setas the sub PCC so that uplink control information is transmitted on theuplink control channel of the above one CC.

Also, as described with reference to FIGS. 17 to 20, the terminal device300 (for example, the communication control unit 363) may conductoperations such as detecting an RLP or an RLF on the sub PCC,controlling the timer 1 and the timer 2, and executing the aboveprescribed procedure (connection reconfiguration procedure or connectionre-establishment procedure).

(Process Flow: Connection Reconfiguration Procedure)

The connection reconfiguration procedure according to the secondmodification of the present embodiment is the same as the connectionreconfiguration procedure according to the first modification describedwith reference to FIG. 16, for example.

(Process Flow: Connection Re-Establishment Procedure)

FIG. 21 is a flowchart illustrating an example of a diagrammatic flow ofa connection re-establishment procedure according to the secondmodification of the present embodiment. This procedure is conductedafter an RLF is detected on the sub PCC, for example.

First, the terminal device 300 transmits, in the PCC for the terminaldevice 300 (a CC of the macro cell 10), an RRC ConnectionRe-establishment Request with a request to change the sub PCC to themacro base station 100 (S461).

Subsequently, the macro base station 100 transmits, in the PCC for theterminal device 300, an RRC Connection Re-establishment message with acommand for changing the sub PCC to the terminal device 300 (S463).

Subsequently, the terminal device 300 transmits, in the PCC for theterminal device 300, an RRC Connection Re-establishment Complete messageto the macro base station 100 (S465). The procedure then ends.

7. APPLICATIONS

Technology according to the present disclosure is applicable to variousproducts. For example, the macro base station 100 may be realized as anevolved Node B (eNB). Conversely, the macro base station 100 may also berealized as another type of base station, such as a NodeB or a basetransceiver station (BTS). The macro base station 100 may also include amain unit that controls radio communication (also called a base stationdevice), and one or more remote radio heads (RRHs) placed in a locationseparate from the main unit.

In addition, the terminal device 300 may be realized as, for example, amobile terminal such as a smartphone, a tablet personal computer (PC), anotebook PC, a portable game console, a portable/dongle-style mobilerouter, or a digital camera, or as an in-vehicle terminal such as a carnavigation device. In addition, the terminal device 300 may also berealized as a terminal that conducts machine-to-machine (M2M)communication (also called a machine-type communication (MTC) terminal).Furthermore, the terminal device 300 may be a radio communication modulemounted onboard these terminals (for example, an integrated circuitmodule configured on a single die).

<7.1. Application Examples Regarding Base Station>

First Application Example

FIG. 22 is a block diagram illustrating a first example of a schematicconfiguration of an eNB to which the technology of the presentdisclosure may be applied. An eNB 800 includes one or more antennas 810and a base station apparatus 820. Each antenna 810 and the base stationapparatus 820 may be connected to each other via an RF cable.

Each of the antennas 810 includes a single or multiple antenna elements(such as multiple antenna elements included in an MIMO antenna), and isused for the base station apparatus 820 to transmit and receive radiosignals. The eNB 800 may include the multiple antennas 810, asillustrated in FIG. 22. For example, the multiple antennas 810 may becompatible with multiple frequency bands used by the eNB 800. AlthoughFIG. 22 illustrates the example in which the eNB 800 includes themultiple antennas 810, the eNB 800 may also include a single antenna810.

The base station apparatus 820 includes a controller 821, a memory 822,a network interface 823, and a radio communication interface 825.

The controller 821 may be, for example, a CPU or a DSP, and operatesvarious functions of a higher layer of the base station apparatus 820.For example, the controller 821 generates a data packet from data insignals processed by the radio communication interface 825, andtransfers the generated packet via the network interface 823. Thecontroller 821 may bundle data from multiple base band processors togenerate the bundled packet, and transfer the generated bundled packet.The controller 821 may have logical functions of performing control suchas radio resource control, radio bearer control, mobility management,admission control, and scheduling. The control may be performed incorporation with an eNB or a core network node in the vicinity. Thememory 822 includes RAM and ROM, and stores a program that is executedby the controller 821, and various types of control data (such as aterminal list, transmission power data, and scheduling data).

The network interface 823 is a communication interface for connectingthe base station apparatus 820 to a core network 824. The controller 821may communicate with a core network node or another eNB via the networkinterface 823. In that case, the eNB 800, and the core network node orthe other eNB may be connected to each other through a logical interface(such as an Si interface and an X2 interface). The network interface 823may also be a wired communication interface or a radio communicationinterface for radio backhaul. If the network interface 823 is a radiocommunication interface, the network interface 823 may use a higherfrequency band for radio communication than a frequency band used by theradio communication interface 825.

The radio communication interface 825 supports any cellularcommunication scheme such as Long Term Evolution (LTE) and LTE-Advanced,and provides radio connection to a terminal positioned in a cell of theeNB 800 via the antenna 810. The radio communication interface 825 maytypically include, for example, a baseband (BB) processor 826 and an RFcircuit 827. The BB processor 826 may perform, for example,encoding/decoding, modulating/demodulating, andmultiplexing/demultiplexing, and performs various types of signalprocessing of layers (such as L1, medium access control (MAC), radiolink control (RLC), and a packet data convergence protocol (PDCP)). TheBB processor 826 may have a part or all of the above-described logicalfunctions instead of the controller 821. The BB processor 826 may be amemory that stores a communication control program, or a module thatincludes a processor and a related circuit configured to execute theprogram. Updating the program may allow the functions of the BBprocessor 826 to be changed. The module may be a card or a blade that isinserted into a slot of the base station apparatus 820. Alternatively,the module may also be a chip that is mounted on the card or the blade.Meanwhile, the RF circuit 827 may include, for example, a mixer, afilter, and an amplifier, and transmits and receives radio signals viathe antenna 810.

The radio communication interface 825 may include the multiple BBprocessors 826, as illustrated in FIG. 22. For example, the multiple BBprocessors 826 may be compatible with multiple frequency bands used bythe eNB 800. The radio communication interface 825 may include themultiple RF circuits 827, as illustrated in FIG. 22. For example, themultiple RF circuits 827 may be compatible with multiple antennaelements. Although FIG. 22 illustrates the example in which the radiocommunication interface 825 includes the multiple BB processors 826 andthe multiple RF circuits 827, the radio communication interface 825 mayalso include a single BB processor 826 or a single RF circuit 827.

Second Application Example

FIG. 23 is a block diagram illustrating a second example of a schematicconfiguration of an eNB to which the technology of the presentdisclosure may be applied. An eNB 830 includes one or more antennas 840,a base station apparatus 850, and an RRH 860. Each antenna 840 and theRRH 860 may be connected to each other via an RF cable. The base stationapparatus 850 and the RRH 860 may be connected to each other via a highspeed line such as an optical fiber cable.

Each of the antennas 840 includes a single or multiple antenna elements(such as multiple antenna elements included in an MIMO antenna), and isused for the RRH 860 to transmit and receive radio signals. The eNB 830may include the multiple antennas 840, as illustrated in FIG. 23. Forexample, the multiple antennas 840 may be compatible with multiplefrequency bands used by the eNB 830. Although FIG. 23 illustrates theexample in which the eNB 830 includes the multiple antennas 840, the eNB830 may also include a single antenna 840.

The base station apparatus 850 includes a controller 851, a memory 852,a network interface 853, a radio communication interface 855, and aconnection interface 857. The controller 851, the memory 852, and thenetwork interface 853 are the same as the controller 821, the memory822, and the network interface 823 described with reference to FIG. 22.

The radio communication interface 855 supports any cellularcommunication scheme such as LTE and LTE-Advanced, and provides radiocommunication to a terminal positioned in a sector corresponding to theRRH 860 via the RRH 860 and the antenna 840. The radio communicationinterface 855 may typically include, for example, a BB processor 856.The BB processor 856 is the same as the BB processor 826 described withreference to FIG. 22, except the BB processor 856 is connected to the RFcircuit 864 of the RRH 860 via the connection interface 857. The radiocommunication interface 855 may include the multiple BB processors 856,as illustrated in FIG. 23. For example, the multiple BB processors 856may be compatible with multiple frequency bands used by the eNB 830.Although FIG. 23 illustrates the example in which the radiocommunication interface 855 includes the multiple BB processors 856, theradio communication interface 855 may also include a single BB processor856.

The connection interface 857 is an interface for connecting the basestation apparatus 850 (radio communication interface 855) to the RRH860. The connection interface 857 may also be a communication module forcommunication in the above-described high speed line that connects thebase station apparatus 850 (radio communication interface 855) to theRRH 860.

The RRH 860 includes a connection interface 861 and a radiocommunication interface 863.

The connection interface 861 is an interface for connecting the RRH 860(radio communication interface 863) to the base station apparatus 850.The connection interface 861 may also be a communication module forcommunication in the above-described high speed line.

The radio communication interface 863 transmits and receives radiosignals via the antenna 840. The radio communication interface 863 maytypically include, for example, the RF circuit 864. The RF circuit 864may include, for example, a mixer, a filter, and an amplifier, andtransmits and receives radio signals via the antenna 840. The radiocommunication interface 863 may include multiple RF circuits 864, asillustrated in FIG. 23. For example, the multiple RF circuits 864 maysupport multiple antenna elements. Although FIG. 23 illustrates theexample in which the radio communication interface 863 includes themultiple RF circuits 864, the radio communication interface 863 may alsoinclude a single RF circuit 864.

In the eNB 800 and the eNB 830 illustrated in FIGS. 22 and 23, theinformation acquisition unit 151 and the communication control unit 153described by using FIG. 6 may be implemented by the radio communicationinterface 825, and the radio communication interface 855 and/or theradio communication interface 863. At least a part of the functions mayalso be implemented by the controller 821 and the controller 851.

<7.2. Application Examples Regarding Terminal Apparatus>

First Application Example

FIG. 24 is a block diagram illustrating an example of a schematicconfiguration of a smartphone 900 to which the technology of the presentdisclosure may be applied. The smartphone 900 includes a processor 901,a memory 902, a storage 903, an external connection interface 904, acamera 906, a sensor 907, a microphone 908, an input device 909, adisplay device 910, a speaker 911, a radio communication interface 912,one or more antenna switches 915, one or more antennas 916, a bus 917, abattery 918, and an auxiliary controller 919.

The processor 901 may be, for example, a CPU or a system on a chip(SoC), and controls functions of an application layer and another layerof the smartphone 900. The memory 902 includes RAM and ROM, and stores aprogram that is executed by the processor 901, and data. The storage 903may include a storage medium such as a semiconductor memory and a harddisk. The external connection interface 904 is an interface forconnecting an external device such as a memory card and a universalserial bus (USB) device to the smartphone 900.

The camera 906 includes an image sensor such as a charge coupled device(CCD) and a complementary metal oxide semiconductor (CMOS), andgenerates a captured image. The sensor 907 may include a group ofsensors such as a measurement sensor, a gyro sensor, a geomagneticsensor, and an acceleration sensor. The microphone 908 converts soundsthat are input to the smartphone 900 to audio signals. The input device909 includes, for example, a touch sensor configured to detect touchonto a screen of the display device 910, a keypad, a keyboard, a button,or a switch, and receives an operation or an information input from auser. The display device 910 includes a screen such as a liquid crystaldisplay (LCD) and an organic light-emitting diode (OLED) display, anddisplays an output image of the smartphone 900. The speaker 911 convertsaudio signals that are output from the smartphone 900 to sounds.

The radio communication interface 912 supports any cellularcommunication scheme such as LTE and LTE-Advanced, and performs radiocommunication. The radio communication interface 912 may typicallyinclude, for example, a BB processor 913 and an RF circuit 914. The BBprocessor 913 may perform, for example, encoding/decoding,modulating/demodulating, and multiplexing/demultiplexing, and performsvarious types of signal processing for radio communication. Meanwhile,the RF circuit 914 may include, for example, a mixer, a filter, and anamplifier, and transmits and receives radio signals via the antenna 916.The radio communication interface 912 may also be a one chip module thathas the BB processor 913 and the RF circuit 914 integrated thereon. Theradio communication interface 912 may include the multiple BB processors934 and the multiple RF circuits 914, as illustrated in FIG. 24.Although FIG. 24 illustrates the example in which the radiocommunication interface 912 includes the multiple BB processors 913 andthe multiple RF circuits 914, the radio communication interface 912 mayalso include a single BB processor 913 or a single RF circuit 914.

Furthermore, in addition to a cellular communication scheme, the radiocommunication interface 912 may support another type of radiocommunication scheme such as a short-distance wireless communicationscheme, a near field communication scheme, and a radio local areanetwork (LAN) scheme. In that case, the radio communication interface912 may include the BB processor 913 and the RF circuit 914 for eachradio communication scheme.

Each of the antenna switches 915 switches connection destinations of theantennas 916 among multiple circuits (such as circuits for differentradio communication schemes) included in the radio communicationinterface 912.

Each of the antennas 916 includes a single or multiple antenna elements(such as multiple antenna elements included in an MIMO antenna), and isused for the radio communication interface 912 to transmit and receiveradio signals. The smartphone 900 may include the multiple antennas 916,as illustrated in FIG. 24. Although FIG. 24 illustrates the example inwhich the smartphone 900 includes the multiple antennas 916, thesmartphone 900 may also include a single antenna 916.

Furthermore, the smartphone 900 may include the antenna 916 for eachradio communication scheme. In that case, the antenna switches 915 maybe omitted from the configuration of the smartphone 900.

The bus 917 connects the processor 901, the memory 902, the storage 903,the external connection interface 904, the camera 906, the sensor 907,the microphone 908, the input device 909, the display device 910, thespeaker 911, the radio communication interface 912, and the auxiliarycontroller 919 to each other. The battery 918 supplies power to blocksof the smartphone 900 illustrated in FIG. 24 via feeder lines, which arepartially shown as dashed lines in the figure. The auxiliary controller919 operates a minimum necessary function of the smartphone 900, forexample, in a sleep mode.

In the smartphone 900 illustrated in FIG. 24, the informationacquisition unit 361 and the communication control unit 363 described byusing FIG. 10 may be implemented by the radio communication interface912. At least a part of the functions may also be implemented by theprocessor 901 or the auxiliary controller 919.

Second Application Example

FIG. 25 is a block diagram illustrating an example of a schematicconfiguration of a car navigation apparatus 920 to which the technologyof the present disclosure may be applied. The car navigation apparatus920 includes a processor 921, a memory 922, a global positioning system(GPS) module 924, a sensor 925, a data interface 926, a content player927, a storage medium interface 928, an input device 929, a displaydevice 930, a speaker 931, a radio communication interface 933, one ormore antenna switches 936, one or more antennas 937, and a battery 938.

The processor 921 may be, for example, a CPU or a SoC, and controls anavigation function and another function of the car navigation apparatus920. The memory 922 includes RAM and ROM, and stores a program that isexecuted by the processor 921, and data.

The GPS module 924 uses GPS signals received from a GPS satellite tomeasure a position (such as latitude, longitude, and altitude) of thecar navigation apparatus 920. The sensor 925 may include a group ofsensors such as a gyro sensor, a geomagnetic sensor, and an air pressuresensor. The data interface 926 is connected to, for example, anin-vehicle network 941 via a terminal that is not shown, and acquiresdata generated by the vehicle, such as vehicle speed data.

The content player 927 reproduces content stored in a storage medium(such as a CD and a DVD) that is inserted into the storage mediuminterface 928. The input device 929 includes, for example, a touchsensor configured to detect touch onto a screen of the display device930, a button, or a switch, and receives an operation or an informationinput from a user. The display device 930 includes a screen such as aLCD or an OLED display, and displays an image of the navigation functionor content that is reproduced. The speaker 931 outputs sounds of thenavigation function or the content that is reproduced.

The radio communication interface 933 supports any cellularcommunication scheme such as LET and LTE-Advanced, and performs radiocommunication. The radio communication interface 933 may typicallyinclude, for example, a BB processor 934 and an RF circuit 935. The BBprocessor 934 may perform, for example, encoding/decoding,modulating/demodulating, and multiplexing/demultiplexing, and performsvarious types of signal processing for radio communication. Meanwhile,the RF circuit 935 may include, for example, a mixer, a filter, and anamplifier, and transmits and receives radio signals via the antenna 937.The radio communication interface 933 may be a one chip module havingthe BB processor 934 and the RF circuit 935 integrated thereon. Theradio communication interface 933 may include the multiple BB processors934 and the multiple RF circuits 935, as illustrated in FIG. 25.Although FIG. 25 illustrates the example in which the radiocommunication interface 933 includes the multiple BB processors 934 andthe multiple RF circuits 935, the radio communication interface 933 mayalso include a single BB processor 934 or a single RF circuit 935.

Furthermore, in addition to a cellular communication scheme, the radiocommunication interface 933 may support another type of radiocommunication scheme such as a short-distance wireless communicationscheme, a near field communication scheme, and a radio LAN scheme. Inthat case, the radio communication interface 933 may include the BBprocessor 934 and the RF circuit 935 for each radio communicationscheme.

Each of the antenna switches 936 switches connection destinations of theantennas 937 among multiple circuits (such as circuits for differentradio communication schemes) included in the radio communicationinterface 933.

Each of the antennas 937 includes a single or multiple antenna elements(such as multiple antenna elements included in an MIMO antenna), and isused for the radio communication interface 933 to transmit and receiveradio signals. The car navigation apparatus 920 may include the multipleantennas 937, as illustrated in FIG. 25. Although FIG. 25 illustratesthe example in which the car navigation apparatus 920 includes themultiple antennas 937, the car navigation apparatus 920 may also includea single antenna 937.

Furthermore, the car navigation apparatus 920 may include the antenna937 for each radio communication scheme. In that case, the antennaswitches 936 may be omitted from the configuration of the car navigationapparatus 920.

The battery 938 supplies power to blocks of the car navigation apparatus920 illustrated in FIG. 25 via feeder lines that are partially shown asdashed lines in the figure. The battery 938 accumulates power suppliedform the vehicle.

In the car navigation apparatus 920 illustrated in FIG. 25, theinformation acquisition unit 361 and the communication control unit 363described by using FIG. 10 may be implemented by the radio communicationinterface 933. At least a part of the functions may also be implementedby the processor 921.

The technology of the present disclosure may also be realized as anin-vehicle system (or a vehicle) 940 including one or more blocks of thecar navigation apparatus 920, the in-vehicle network 941, and a vehiclemodule 942. The vehicle module 942 generates vehicle data such asvehicle speed, engine speed, and trouble information, and outputs thegenerated data to the in-vehicle network 941.

8. CONCLUSION

The foregoing thus describes an embodiment of the present disclosurewith reference to FIGS. 5 to 25. According to an embodiment of thepresent disclosure, the macro base station 100 is equipped with aninformation acquisition unit 151 that acquires information about aterminal device using one CC of a macro cell 10 as the PCC, and acommunication control unit 153 that sets one or more CCs of a small cell20 as additional CCs to be used additionally by the terminal device. Thecommunication control unit 153 sets one CC among the above one or moreCCs as the sub PCC (that is, a special CC on which the above terminaldevice is able to transmit uplink control information on an uplinkcontrol channel).

Consequently, for example, it becomes possible to reduce the effect ofbackhauling on wireless communications in the case of carrieraggregation.

More specifically, ordinarily uplink control information on an uplinkcontrol channel is not transmitted by an SCC, and instead, uplinkcontrol information for an SCC is transmitted on an uplink controlchannel of the PCC. For this reason, if the SCC is a CC of the smallcell 20 and the PCC is a CC of the macro cell 10, a delay on thebackhaul may cause uplink control information for an SCC to take a longtime to reach the small base station 200. Accordingly, as discussedabove, one CC of the small cell 20 is set as the sub PCC. Uplink controlinformation is then transmitted on the uplink control channel of the subPCC. Consequently, the effect of backhauling on wireless communicationsis reduced, for example.

Uplink Control Information

For example, the above uplink control information includes anacknowledgement (ACK) and a negative acknowledgement (NACK) regardingthe reception of a downlink signal.

Consequently, for example, since an ACK/NACK is transmitted on theuplink control channel of the sub PCC, the ACK/NACK reaches the smallbase station 200 quickly. Consequently, suitable retransmission controlmay be possible.

Additionally, the above uplink control information includes a schedulingrequest (SR), for example.

Consequently, for example, since a scheduling request is transmitted onthe uplink control channel (PUCCH) of the sub PCC, the schedulingrequest reaches the small base station 200 quickly. Consequently, rapidscheduling may be possible.

Additionally, the above uplink control information includes periodicallyreported channel state information (CSI), for example.

Consequently, for example, since periodically reported CSI istransmitted on the uplink control channel (PUCCH) of the sub PCC, theCSI reaches the small base station 200 quickly. Consequently, rapidadaptation of the wireless communications of the above terminal deviceto the environment may be possible.

Uplink Control Channel

The above uplink control channel is the PUCCH, for example.

Consequently, for example, since uplink control information transmittedon the PUCCH is transmitted on the PUCCH of the sub PCC, the relevantuplink control signal may reach the small base station 200 quickly.

Notification of Addition of Sub PCC

When newly setting a CC of the small cell 20 as an additional CC to beused by a terminal device, if the relevant CC is set as the sub PCC, thecommunication control unit 153 notifies the above terminal device thatthe relevant CC is added as the sub PCC.

Consequently, for example, a terminal device using a CC of the macrocell 10 as the PCC becomes able to learn which CC is the sub PCC for therelevant terminal device. For this reason, the relevant terminal devicebecomes able to actually transmit uplink control information on theuplink control channel of the sub PCC. Note that since the terminaldevice conducts procedures such as the Connection Establishmentprocedure on the PCC, the PCC is self-evident to the terminal device,but since the terminal device does not conduct procedures such as theConnection Establishment procedure on the sub PCC, the sub PCC is notself-evident to the terminal device. For this reason, a notificationlike the above is particularly effective.

Setting SCC Associated with Sub PCC

For example, the communication control unit 153 sets a CC not set as thesub PCC from among the above one or more CCs of the small cell 20 (thatis, the one or more CCs set as the above additional CCs) as an SCCassociated with the sub PCC. An SCC associated with the sub PCC is a CCby which a terminal device is unable to transmit the above uplinkcontrol information on the above uplink control channel. The aboveuplink control information for an SCC associated with the sub PCC istransmitted on the above uplink control channel of the sub PCC.

Consequently, for example, not only uplink control information for thesub PCC but also uplink control information for an SCC associated withthe sub PCC may be transmitted on the uplink control channel of the subPCC. Consequently, the effect of backhauling on wireless communicationsmay be reduced further, for example.

Notification of Addition of SCC Associated with Sub PCC

For example, when newly setting a CC of the small cell 20 as anadditional CC to be used by a terminal device, if the relevant CC is setas an SCC associated with the sub PCC, the communication control unit153 notifies the above terminal device that the relevant CC is added asan SCC associated with the sub PCC.

Accordingly, for example, a terminal device using a CC of the macro cell10 as the PCC becomes able to learn which CC is an SCC associated withthe sub PCC. For this reason, the relevant terminal device becomes ableto actually transmit uplink control information for the relevant SCC onthe uplink control channel of the sub PCC.

Setting (Changing) Sub PCC

According to the first modification of the present embodiment, thecommunication control unit 153 changes the sub PCC by newly setting, asthe sub PCC, one CC currently set as an SCC associated with the sub PCC.

Consequently, for example, changing the sub PCC does not require acomplicated procedure like a handover, unlike changing the PCC. For thisreason, the sub PCC may be changed with a reduced burden, for example.

Association with Sub PCC after Change of Sub PCC

According to the first modification of the present embodiment, forexample, after the change of the sub PCC, another CC set as an SCCassociated with the sub PCC is associated with the above one CC newlyset as the sub PCC.

Consequently, for example, even if the sub PCC is changed, an SCCassociated with the sub PCC is not released, removed, or deactivated,but instead continues to be used. For this reason, re-adding a CC is notnecessary, and thus the burden may be reduced. In other words, the subPCC may be changed with a reduced burden.

Notification of Change of Sub PCC

According to the first modification of the present embodiment, forexample, during the change of the sub PCC, the communication controlunit 153 notifies the above terminal device that the sub PCC is changedto the above one CC newly set as the sub PCC.

Accordingly, for example, a terminal device using a CC of the macro cell10 as the PCC becomes able to learn of the change of the sub PCC. Forthis reason, the relevant terminal device becomes able to actuallytransmit uplink control information on the uplink control channel of thesub PCC after the change of the sub PCC.

Setting (Changing) Sub PCC

According to the second modification of the present embodiment, forexample, if a radio link failure (RLF) occurs on the sub PCC, thecommunication control unit 153 newly sets one CC currently set as an SCCassociated with the sub PCC as the sub PCC via a prescribed procedure.

Consequently, for example, even if an RLF occurs on the sub PCC and thesub PCC becomes unusable, an SCC that was associated with the sub PCCmay continue to be used. For this reason, communication quality may beimproved, for example.

On the other hand, for example, if the above prescribed procedure doesnot complete within a prescribed period, the communication control unit153 stops usage of the sub PCC and the SCC associated with the sub PCCby the above terminal device.

Consequently, for example, even though communication on the sub PCC isdifficult, continued usage of the sub PCC may be avoided. As anotherexample, even though transmitting uplink control information for an SCCassociated with the sub PCC (such as an ACK/NACK, a scheduling request,and periodically reported CSI) is difficult, continued usage of theabove SCC may be avoided. As a result, wireless communicationsassociated with degraded communication quality may be stopped rapidly.

Conditions of Setting

Also, for example, if the backhaul between the macro base station 100and the small base station 200 does not satisfy a prescribed qualitystandard, the communication control unit 153 sets the above one CC amongthe above one or more CCs of the small cell 20 as the sub PCC.

Consequently, it becomes possible to set the sub PCC in cases where thedelay on the backhaul may become large, for example.

Also, if the backhaul between the macro base station 100 and the smallbase station 200 satisfies a prescribed quality standard, thecommunication control unit 153 sets each of the above one or more CCs ofthe small cell 20 as an SCC associated with the PCC.

Consequently, for example, if a small delay on the backhaul isanticipated, it becomes possible to treat the CCs of the small cell asSCCs associated with the PCC. For this reason, the small base station200 may be dedicated to transmitting and receiving data, for example. Asa result, throughput in the small cell 20 may be improved.

The preferred embodiment(s) of the present disclosure has/have beendescribed above with reference to the accompanying drawings, whilst thepresent disclosure is not limited to the above examples, of course. Aperson skilled in the art may find various alterations and modificationswithin the scope of the appended claims, and it should be understoodthat they will naturally come under the technical scope of the presentdisclosure.

For example, an example is described in which a CC (for example, the subPCC) is set by updating the setting information indicating a CC to beused by a terminal device, but the present disclosure is not limited tosuch an example. For example, the above setting information may also beother information about a CC to be used by a terminal device, and notinformation indicating a CC to be used by a terminal device. Also, a CC(for example, the sub PCC) may be set by a method other than updatingsetting information. In other words, a CC may be set by some othermethod enabling a CC to be used.

In addition, an example is described in which the sub PCC is set if thebackhaul between the macro cell and the small cell does not satisfy theprescribed quality standard, and the sub PCC is not set otherwise, butthe present disclosure is not limited to such an example. For example,one CC of the small cell may also be set as the sub PCC, irrespectivelyof the above backhaul.

In addition, an example is described in which, if a CC of the macro cellis the PCC and a CC of the small cell is the sub PCC, another CC of therelevant small cell is set as an SCC associated with the sub PCC, butthe present disclosure is not limited to such an example. For example,the above other CC may also be set as an SCC associated with the PCC. Asanother example, a first CC of the above small cell may be set as an SCCassociated with the PCC, while a second CC of the above small cell maybe set as an SCC associated with the sub PCC.

In addition, an example in which a CC of the macro cell becomes the PCCis primarily described, but the present disclosure is not limited tosuch an example. For example, a CC of the small cell may also become thePCC. In this case, none of the CCs of the relevant small cell needs tobe set as the sub PCC.

In addition, an example is described in which the terminal device usesthe CCs of one small cell, but the present disclosure is not limited tosuch an example. For example, the terminal device may also use the CCsof multiple small cells simultaneously. In this case, a sub PCC may beset for each of the multiple small cells, or a common sub PCC may be setfor two or more small cells among the multiple small cells.

In addition, an example is described in which the macro base stationperforms the acquisition of information about the terminal device usingone CC of the macro cell as the PCC and the setting of the sub PCC, butthe present disclosure is not limited to such an example. For example,any core network node may perform the above acquisition and the abovesetting. Alternatively, the small base station may perform the aboveacquisition and the above setting. In other words, the informationacquisition unit and the communication control unit of the macro basestation discussed earlier may also be provided by a core network node orthe small base station instead of being provided by the macro basestation.

Although an example is described in which the communication system is asystem conforming to LTE, LTE-Advanced, or a compliant communicationscheme, the present disclosure is not limited to such an example. Forexample, the communication system may be a system conforming to anothercommunication standard.

Also, the processing steps in each process in this specification are notstrictly limited to being executed in a time series following thesequence described in a flowchart. For example, the processing steps ineach process may be executed in a sequence that differs from a sequencedescribed herein as a flowchart, and furthermore may be executed inparallel.

In addition, it is possible to create a computer program for causinghardware such as a CPU, ROM, and RAM built into a device according to anembodiment of the present disclosure (a communication control device ora terminal device) to exhibit functions similar to each structuralelement of the foregoing devices. Also, a storage medium having such acomputer program stored therein may also be provided. Also, aninformation processing device (for example, a processing circuit orchip) equipped with memory storing such a computer program (for example,ROM and RAM) and one or more processors capable of executing such acomputer program (such as a CPU or DSP, for example) may also beprovided.

In addition, the advantageous effects described in this specificationare merely for the sake of explanation or illustration, and are notlimiting. In other words, instead of or in addition to the aboveadvantageous effects, technology according to the present disclosure mayexhibit other advantageous effects that are clear to persons skilled inthe art from the description of this specification.

Additionally, the present technology may also be configured as below.

(1)

A communication control device including:

an acquisition unit configured to acquire information about a terminaldevice that uses one component carrier of a macro cell as a primarycomponent carrier; and

a control unit configured to set one or more component carriers of asmall cell partially or fully overlapping with the macro cell as anadditional component carrier to be used additionally by the terminaldevice, wherein

the control unit sets one component carrier among the one or morecomponent carriers as a special component carrier on which the terminaldevice is able to transmit uplink control information on an uplinkcontrol channel.

(2)

The communication control device according to (1), wherein

the uplink control information includes an acknowledgement (ACK) and anegative acknowledgement (NACK) regarding reception of a downlinksignal.

(3)

The communication control device according to (1) or (2), wherein theuplink control information includes an uplink scheduling request.

(4)

The communication control device according to any one of (1) to (3),wherein

the uplink control information includes periodically reported channelstate information.

(5)

The communication control device according to any one of (1) to (4),wherein the uplink control channel is a physical uplink control channel(PUCCH).

(6)

The communication control device according to any one of (1) to (5),wherein

the special component carrier is a component carrier on which aconnection establishment procedure is not conducted by the terminaldevice.

(7)

The communication control device according to any one of (1) to (6),wherein

the special component carrier is a component carrier selected for eachterminal device.

(8)

The communication control device according to any one of (1) to (7),wherein

when newly setting a component carrier of the small cell as theadditional component carrier, if the control unit sets the relevantcomponent carrier as the special component carrier, the control unitnotifies the terminal device of the addition of the component carrier asthe special component carrier.

(9)

The communication control device according to any one of (1) to (8),wherein

the control unit sets a component carrier not set as the specialcomponent carrier from among the one or more component carriers of thesmall cell as a secondary component carrier associated with the specialcomponent carrier,

the secondary component carrier is a component carrier on which theterminal device is unable to transmit the uplink control information onthe uplink control channel, and

the uplink control information related to the secondary componentcarrier is information transmitted on the uplink control channel of thespecial component carrier.

(10)

The communication control device according to (9), wherein

when newly setting a component carrier of the small cell as theadditional component carrier, if the control unit sets the relevantcomponent carrier as the secondary component carrier, the control unitnotifies the terminal device of the addition of the component carrier asthe secondary component carrier.

(11)

The communication control device according to (9) or (10), wherein

the control unit changes the special component carrier by newly setting,as the special component carrier, one component carrier currently set asthe secondary component carrier.

(12)

The communication control device according to (11), wherein

after the special component carrier is changed, another componentcarrier currently set as the secondary component carrier is associatedwith the one component carrier newly set as the special componentcarrier.

(13)

The communication control device according to (11) or (12), wherein

when changing the special component carrier, the control unit notifiesthe terminal device that the special component carrier is changed to theone component carrier newly set as the special component carrier.

(14)

The communication control device according to (13), wherein

the control unit notifies the terminal device that the special componentcarrier is changed to the one component carrier newly set as the specialcomponent carrier in a message during a connection reconfigurationprocedure.

(15)

The communication control device according to any one of (11) to (14),wherein

if a radio link failure occurs on the special component carrier, thecontrol unit newly sets, as the special component carrier, one componentcarrier currently set as the secondary component carrier, via aprescribed procedure.

(16)

The communication control device according to (15), wherein

the prescribed procedure is a connection reconfiguration procedure or aconnection re-establishment procedure for changing the special componentcarrier.

(17)

The communication control device according to (15) or (16), wherein

if the prescribed procedure does not complete within a prescribedperiod, the control unit stops usage of the special component carrierand the secondary component carrier associated with the specialcomponent carrier by the terminal device.

(18)

The communication control device according to any one of (11) to (17),wherein

if a backhaul between a base station of the macro cell and a basestation of the small cell does not satisfy a prescribed qualitystandard, the control unit sets the one component carrier among the oneor more component carriers as the special component carrier, whereas ifthe backhaul satisfies the prescribed quality standard, the control unitsets each of the one or more component carriers as a secondary componentcarrier associated with the primary component carrier.

(19)

A communication control method including:

acquiring information about a terminal device that uses one componentcarrier of a macro cell as a primary component carrier; and

setting, by a processor, one or more component carriers of a small cellpartially or fully overlapping with the macro cell as an additionalcomponent carrier to be used additionally by the terminal device,wherein

the setting of the one or more component carriers as the additionalcomponent carrier includes setting one component carrier among the oneor more component carriers as a special component carrier on which theterminal device is able to transmit uplink control information on anuplink control channel.

(20)

A terminal device including:

an acquisition unit configured to acquire, when the terminal device usesone component carrier of a macro cell as a primary component carrier,one or more component carriers of a small cell partially or fullyoverlapping with the macro cell are set as an additional componentcarrier to be used additionally by the terminal device, and onecomponent carrier among the one or more component carriers is set as aspecial component carrier on which the terminal device is able totransmit uplink control information on an uplink control channel,information about the one component carrier; and

a control unit configured to control wireless communication on the onecomponent carrier so that the uplink control information is transmittedon the uplink control channel of the one component carrier.

REFERENCE SIGNS LIST

-   1 communication system-   10 macro cell-   20 small cell-   100 macro base station-   151 information acquisition unit-   153 communication control unit-   200 small base station-   300 terminal device-   361 information acquisition unit-   363 communication control unit

1. A method for a first base station, the method comprising: controllinga Radio Resource Control (RRC) connection with a user equipment thataggregates: a first component carrier, as a primary component carrier,served by the first base station, and a second component carrier, as aspecial component carrier on which uplink control information istransmitted, served by a second base station, wherein the specialcomponent carrier is not used to establish the RRC connection; andsending, to the user equipment via the primary component carrier, a RRCconnection reconfiguration message, the RRC connection reconfigurationmessage including information indicating that the special componentcarrier assigned to the user equipment is changed from the secondcomponent carrier to a third component carrier served by the second basestation.
 2. The method according to claim 1, the method furthercomprising: receiving, from the user equipment, an RRC message includinginformation indicating that a timer to detect radio link failure on thespecial component carrier has expired, wherein the RRC connectionreconfiguration message for changing the special component carrierassigned to the user equipment is sent, after the radio link failure onthe second component carrier as the special component carrier isdetected by the user equipment.
 3. The method according to claim 2,wherein the uplink control information includes at least one of: anacknowledgement (ACK) and a negative acknowledgement (NACK) regardingreception of a downlink signal on one or more component carriers.including the second component carrier and the third component carrier,served by the second base station, an uplink scheduling request for theone or more component carriers. including the second component carrierand the third component carrier, served by the second base station, andchannel state information for the one or more component carriers.including the second component carrier and the third component carrier,served by the second base station.
 4. A method for a user equipment, themethod comprising: establishing a Radio Resource Control (RRC)connection on a first component carrier served by a first base station;aggregating: the first component carrier, as a primary componentcarrier, and a second component carrier, as a special component carrieron which uplink control information is transmitted, served by a secondbase station, wherein the special component carrier is not used toestablish the RRC connection; and receiving, from the first base stationvia the primary component carrier, a RRC connection reconfigurationmessage, the RRC connection reconfiguration message includinginformation indicating that the special component carrier assigned tothe user equipment is changed from the second component carrier to athird component carrier served by the second base station.
 5. The methodaccording to claim 4, wherein the method further comprising: sending, tothe first base station, an RRC message including information indicatingthat a timer to detect radio link failure on the special componentcarrier has expired, wherein the RRC connection reconfiguration messagefor changing the special component carrier assigned to the userequipment is received, after the radio link failure on the secondcomponent carrier as the special component carrier is detected by theuser equipment.
 6. The method according to claim 5, the uplink controlinformation includes at least one of: an acknowledgement (ACK) and anegative acknowledgement (NACK) regarding reception of a downlink signalon one or more component carriers. including the second componentcarrier and the third component carrier, served by the second basestation, an uplink scheduling request for the one or more componentcarriers. including the second component carrier and the third componentcarrier, served by the second base station, and channel stateinformation for the one or more component carriers. including the secondcomponent carrier and the third component carrier, served by the secondbase station.
 7. A first base station comprising: a radio transceiver;and a processor including hardware, the processor configured to: controla Radio Resource Control (RRC) connection with a user equipment thataggregates: a first component carrier, as a primary component carrier,served by the first base station, and a second component carrier, as aspecial component carrier on which uplink control information istransmitted, served by a second base station, wherein the specialcomponent carrier is not used to establish the RRC connection; and send,to the user equipment via the primary component carrier, a RRCconnection reconfiguration message, the RRC connection reconfigurationmessage including information indicating that the special componentcarrier assigned to the user equipment is changed from the secondcomponent carrier to a third component carrier served by the second basestation.
 8. A user equipment comprising: a radio transceiver; and aprocessor including hardware, the processor configured to: establish aRadio Resource Control (RRC) connection on a first component carrierserved by a first base station; aggregate: the first component carrier,as a primary component carrier, and a second component carrier, as aspecial component carrier on which uplink control information istransmitted, served by a second base station, wherein the specialcomponent carrier is not used to establish the RRC connection; andreceive, from the first base station via the primary component carrier,a RRC connection reconfiguration message, the RRC connectionreconfiguration message including information indicating that thespecial component carrier assigned to the user equipment is changed fromthe second component carrier to a third component carrier served by thesecond base station.